1. Field of the Invention
The invention generally relates to suspension systems and more particularly to an improved air spring unit particularly suited for use with a spring suspension system mounted on a live axle of a type currently provided for wheeled vehicles, such as trucks and the like.
2. Description of the Prior Art
Vehicle suspension systems including coil springs, leaf springs, and the like are notoriously old. However, designers of such suspension systems have long been plagued with the perplexing problem of imparting empty-ride capabilities to such systems. That is to say, that while it is apparent that springs of sufficient rigidity can be provided for supporting a vehicle in its loaded condition, or conversely, in its unloaded condition, a perplexing problem arises when a given vehicle must be employed in its loaded and unloaded condition, alternately.
For example, a flat bed trailer or the like often is employed in delivering a load to a given destination and thereafter returned to the point of origin, or other destination, in an empty condition. Where the springs of the suspension system employed are sufficiently rigid for supporting the trailer as it is transported in its loaded condition, the springs lack sufficient resiliency for overcoming shock-loading when the vehicle is transported in its empty or unloaded condition. The destructive effects of shock-loading can readily be appreciated by those familiar with the trucking industry.
In order to overcome the aforementioned disadvantages of conventional suspension systems, attempts have been made to modify the effects of conventional systems by including air bags and the like in combination therewith. One such modified suspension system is illustrated in U.S. Pat. No. 3,866,894 which issued to Phillip J. Sweet et al., Feb. 18, 1975.
Modified systems generally have met with success, particularly when included in suspension systems for trailers and the like. However, limitations on available space for mounting air bags tend to severely restrict the mounting of relatively large air bags on live axles, particularly where the air bag must be located in the vicinity of the periphery of a wheel and the circumscribing tire.
It is, therefore, the general purpose of the instant invention to provide an improved, economic and efficient air spring unit which is particularly suited for use in modifying conventional suspension systems of the type characterized by cantilevered leaf springs mounted on live axles for vehicles whereby the aforementioned difficulties and disadvantages are substantially overcome without impairing operational capabilities of the vehicles.